Foot Type and Laminitis Incidence in Feral Horses

Horses that roam free in the wild, be they American mustangs, Australian brumbies, or horses from other feral herds, differ from their domestic counterparts in that they receive no food, water, veterinary care, or hoof care from humans. To determine what effect feral horses' natural environments have on hoof type and predisposition toward developing laminitis, Brian Hampson, PhD, of the Australian Brumby Research Unit at the University of Queensland's School of Veterinary Science, tracked brumbies and evaluated their feet visually and radiographically (via X ray). He presented his findings at the 6th International Equine Conference on Laminitis and Diseases of the Foot, held Oct. 28-31 in West Palm Beach, Fla.

This horse frequented sandy deserts...

While this horse frequented rocky deserts.

Hampson and colleagues caught and placed GPS tracking devices on 35 brumbies from six Australian study areas characterized by different environmental conditions (e.g., water sources, food, footing). After tracking the horses' travel patterns for periods of six weeks to six months, the team caught the animals again and downloaded GPS data that revealed how far horses traveled in each environment. With this information Hampson determined that environment has a huge impact on the horses' feet. Additionally, he photographed and radiographed the feet of 100 horses euthanized during routine culling operations and established 40 foot shape and structure parameters for study. Looking at two different foot types in particular--rocky desert versus soft, sandy terrain--he determined Australian brumbies have no "natural" foot type, but rather the environment dictates their hoof characteristics.

As expected, the feet of horses in the rocky environment had worn down, but not necessarily for the better. Radiographs revealed these horses' hoof walls were 19-30 mm thick (domestic horses' thickness is typically 14-18 mm), indicating a stiff hoof type that could lead to foot pathologies; their "sinker" distance was twice that of domestic horses, meaning that the bony skeleton had sunk over time deeper into the outer hoof; and their soles were excessively thick, creating tight, boxy, and heavy feet. The laminae were attenuated, or stretched, and ultimately "sinking" with signs of concussive laminitis was the norm in these animals.

The feet of the brumbies residing and traveling on soft, sandy terrain wore slower than did those of the rocky-environment horses, and their hoof walls were not excessively thick. Instead, they had long toes that broke away naturally. These horses' feet showed no signs of laminitis or other serious foot pathology.

After recording the characteristics of these horses' feet, Hampson then aimed to determine if their foot types could change. He caught 12 horses (six from rocky terrain and six from sandy), radiographed and photographed their feet, and then swapped their environments. He tracked the rocky environment horses via GPS for six months (800 km traveled) in a sandy environment and the sandy environment horses for four months (1,016 km traveled) in the rocky environment. What he discovered was that foot type does depend on environment (e.g., substrate hardness and distance traveled), as both groups of horses' feet changed completely during this time period to match the new host environments.

Hampson also discovered a high incidence of laminitis in four study areas around Australia. Of the euthanized horses he radiographed:

67% of 15 rocky terrain horses were laminitic;

40% of 15 sandy desert horses were laminitic;

93% of 15 prime grazing terrain horses were laminitic;

40% of 56 Kaimanawa region (New Zealand) horses were laminitic.

In the sandy desert and prime grazing areas where lush forage is prevalent after floods and fires, Hampson was not surprised to discover more laminitis cases that likely were pasture-induced. In the rocky area, where horses had more stable diets and traveled long distances, the high laminitis rates were unexpected but were likely due to the horses' concussive environment, increased sole loading, and hard lifestyle from birth. He added that these horses did not appear "overly lame" and still traveled high distances. "It may be that the robust foot structure and the unique foot morphology of these horses is protective against mechanical trauma and the pain often associated with chronic laminitis in domesticated horses," he hypothesized.

Hampson ultimately concluded there is no one natural foot type in horses and, contrary to popular belief, feral horses are not exempt from developing laminitis. Also, "There is currently no clear evidence to support the use of the extreme feral horse foot as a model for equine foot care," he cautioned. Keeping in mind all horses are likely vulnerable to laminitis, Hampson proposed the following suggestions for horse owners:

Maintain appropriate diets;

Don't overtrim horses' feet;

Try to avoid excessive hard surfaces; and

Encourage animals to exercise more, such as by using feeding systems that require horses to move around or by housing horses in large paddocks.

About the Author

Alexandra Beckstett, Managing Editor of The Horse and a native of Houston, Texas, is a lifelong horse owner who has shown successfully on the national hunter/jumper circuit and dabbled in hunter breeding. After graduating from Duke University, she joined Blood-Horse Publications as Assistant Editor of its book division, Eclipse Press, before joining The Horse.

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